Control apparatus for reversible motors



M8111) 18, F, R f-'ARRQQV` JR 2,417,593

CONTRQL APPARATUS POR REVERSIBLE' mns med laren'sl. 1944 Patented Mar. 18, 1947 2,417,593 @@NTRL PERATS FOR REVERSIBLE MOTORS Frederick R. Farrow, Jr., Audubon, N. J., assignor, by mesne assignments, to Philco Corporation,

Philadelphia, Vania Pa., a corporation of Pennsyl- Application March 31, 1944, Serial No. 528,898

1li Claims.. i

invention relates to novel system for controlling a reversible motor, and more particularly to novel means effecting controlled periodic reversal of the motor. The invention is particularly 'useful in the control of an. electric Knoten-driven mechanism, such as the scanning `iu'ltenna employed in radio detecting and ranging (radar) systems and the like.

.ln certain systems of this character, the scanning equipment is driven by an electric motor which is, or may be, periodically reversed so that the scanning equipment is driven back and fortis across a desired sector. In some of the sys-n tems heretofore proposed, it has been necessary to utilize two motors, one `tor driving the controlling mechanism, and one for driving the scanidng equipment. paratus for controlling the scanning equipment to be designed soy as to compensate for the normal tendency of a motor to rotate better in direction than in the other, which tendency caused the apparatus to creep in the direction of more efficient motor operation.

.it is an object of the present invention to provide an improved and simplied control mechanism for a reversible motor, especially in a system oi the abovementioned character.

.Another object of the invention is to provide :inotormdriven control apparatus for motor-driven s nning equipment which shall have no tendency to creep @ther objects and advantages will become apparent as the invention is described in ccnnec tion with the accompanying drawing, the single ilgure of which is a diagrammatic illustration of typical control system embodying the principles of the invention.

lin these prior systems the anm doctors t and it. The armature it ci this motor is connected to the same line conductors 8 and lil through the agency of the conductors lil and iS, it and to, and the reversing relay 2t. The reversing relay 22 is preferably of the over center or latching type. Reversing relays of this general character are well known in the art, and consequently it is deemed unnecessary to describe this device in detail. llit will sumce to say that when the movable contactors 24 and 28 are drawn to the rig'ht (as shown) by energize. tion of the relay Winding 28 the said contactors will "latch in that position. will remain in that position until such time as the relay coil 30 is energized. it such time the contactors te and 26 will be drawn to the leit, and will re main latched in that position until such time as relay coil 28 is energized. It will be evident from the drawing that the movable contactera 24 and 26, together with the xed contact points `322, 34, 3S, and constitute a conventional ren verslng switch or relay. Thus, in one position of the movable contactors 24 and 26, the armature l2 of the reversible motor 2 is so connected to the line as to cause rotation of the motor in one direction, while in the other position of the movable contactors 24 and 26, the armature is so connected as to produce motor rotation in the opposite direction.

'lhe armature or rotor l2 of the reversible mem tor may be mechanically coupled, 'by any suit-z able and convenient means, to the scanning de vice 4. In the drawing, this mechanical cou pling is represented by the dashed connecting line. Also mechanically coupled to the reversi ble motor 2, and rotating in synchronisni with the scanning device Il, is a rotating conimutator 4t, preferably constructed of a conducting mate rial, and bearing a suitable contact element 42. Concentrically arranged around the rotating the rotating commutator 4U are a plurality of fixed contact points 44, 46, 48, 5G, 52, and 54. These xed contact points are preferably equally spaced about the rotating commutator, and are so ivositioned with respect thereto that electrical contact is made between the said xed contact points and the contact element 42 as the said element rotates past, or reaches, a given contact point. As shown in the drawing, the rotating commute@ tor is connected by means of a conductor 58 to the conductor lll of the line 8, itl. The speciic function of the rotating ccmmutator t9 will be described in detail hereinafter.

Each of the contact points t4, 46, etc., are connected by means of suitable conductors to the similarly designated Contact points of a pair of manually operable switches 58 and 68. Thus, by way of example. the contact point 44 associated with the rotating commutator 48 is connected by way of the conductor 62 with the contact point 44a of the switch 80, and by way of the conductors 82 and 84 with the contact point 44b of the switch 88. The switches 58 and 80 together comprise what may be referred to as a sector selector," and they are so designated in the drawing. The adjustable contact arm 88 of switch 88 is oonnected by way of the conductor 18 to terminal 82 of the reversing relay coil 28. Similarly the adjustable contact arm 88 of switch 88 is connected by way of conductor 12 to terminal 18 of reversing relay coil 30. The other terminals, 84 and 88, of coils 28 and 80 are connected together by means of the conductor 14, and to the line conductor 8 by way of the conductor 18. Accordingly one terminal of each of the reversing relay coils 28 and 80 is connected permanently and directly to one side of the line 8, l0. Connection between the other terminals of the coils 28 and 88 and the other side of the line is made through the sector selector switches 88 and 88, and the rotating commutator 48.

The component parts and connections illustrated in the drawing having now been described, the operation of the system will now be set forth. Let us assume that it is desired to so operate the scanning device 4 that the sector Si shall be continuously scanned. As indicated, the limits of the sector S1 are defined by the reference characters 44o and 48o. By means of the structure provided by the present invention, such operation is secured by setting the contact arms 88 and 88 of sector selector switches 58 and 88 to corresponding and similarly designated switch contact points.

Thus the contact arm 88 may be adjusted to contact the contact point 48a, while the contact arm 88 is adjusted to contact the contact point 44h. These switch adjustments are illustrated in the drawing. If now the field 8 of the motor 2 is connected in the proper sense to the line conductors 8 and Hl, and this is most conveniently determined by trial, the system will operate as follows. Assume that at the instant represented in the drawing the scanning device 4 and the rotating commutator 40 are being driven synchronously in a clockwise direction by the reversible motor 2. When the contact element 42 of the rotating commutator reaches the contact point 48, a connection will be completed between the line conductor I8 and the terminal 18 of relay coil 30. This connection includes the conductor 88, the rotating commutator 40, contact element 42, contact point 48, conductor 88, contact point 48a, switch arm 88, and the conductor 12. Since terminal 88 of the relay coil 38 is already connected to the other side of the line by way of the conductors 14 and 18, the coil 30 is now energized from the line, and consequently the movable contactors 24 and 28 are moved from the position illustrated to their left-hand position, where they make contact with stationary contacts 82 and I8 respectively, thus reversing the connections between the armature l2 and the' line conductors 8, lil, and thereby reversing the direction of rotation of the motor. The direction of rotation of the scanning device 4 and the rotating commutator 40 are, of course, also reversed, and consequently the rotating commutator 48 now proceeds to rotate in a counter-clockwise direction. This it continues to do until the contact element 42 .4 reaches and makes contact with contact point 44. When this occurs a connection is completed between the line conductor I8 and terminal 82 of relay coil 28. This connection includes the conductor 56, the rotating commutator 40, contact element 42, contact point 44, the conductors 62 and 84, switch arm 88, and the conductor 10. Since the terminal 84 of relay coil 28 is already connected to line conductor 8 by way of the conductors 14 and 18, the coil 28 is energized and movable contactors 24 and 26 are moved from their left-hand position to the right-hand position shown. This effects a second reversal of the motor 2, ,whence the scanning device 4 and the rotating commutator 40 are also reversed and begin rotation in the clockwise direction. The foregoing train of events will now repeat cyclically so-long as the contact arms 88 and 88 of the sector selector switches remain in the positions shown.

It will now be evident that by means of the present invention it is possible to establish, on the sector selector switches 88 and 80, connections corresponding to desired sector limits on the scanning device 4, and thus to eiect continuous scanning over a desired sector. For example, if it is desired to sector-scan the sector S: included within the sector limits 52e and 54e, it is only necessary to adjust the switch arm 88 to contact the contact point B2b and to adjust the switch arm 88 to contact the contact point 54a. Larger sectors may be scanned by adjusting the switch arms 88 and 88 to the contact points corresponding to the limits of the desired sector. Where six contact points are provided, as in the illustration, the smallest sector which can be scanned is a 60 sector. If smaller sectors are desired it is, of course, necessary only to increase the number of contact points associated with the rotating commutator and with the two sector selector switches.

Although it will normally be desired to scan sectors of substantially less than it may, under certain circumstances, be useful to scan sectors of greater than 180. Buch large sectors are as readily scanned with the apparatus illustrated as are the smaller sectors. As has already been stated, with the speciilc adjustment illustrated in the drawing, sector scanning of the device4 is effected over the sector Si. If. now, the. relative positions of the sector selector switches are reversed, i. e., if contact arm 88 is moved to contact 48h and contact arm 88 moved to 44a, the scanning device 4 will sector-scan the sector Ss. It will be observed that the sector Sa has the same limits as the sector S1, but that sector S: is the complement of sector Si.

The scanning apparatus of the drawing has been described, so far, only with reference to its operation as a sector scanning system. As was indicated at the outset, the system illustrated in the drawing is also adapted to effect continuous rotation, in either direction, of the scanning device 4. To this end there may be provided a switch 88 (shown in its closed position) in the conductor 18. This conductor normally connects one terminal of each of the relay coils to the line conductor 8. When the switch 88 is opened the relay coils can no longer be energized throush the rotating commutator and sector selector circuits, and consequently rotation of the scanning device 4 continues in the directionl it had at the moment the switch 88 was opened. The operator can, if he desires, open the switch to give continuous rotation in a selected direction by simdiagrammatically illustrated annees ply observing the movements oi' the scanning dehe opens the switch 88. A

apparent that the invention is not limited to the specific purpose illustrated and described but may be utilized in any instance where it is desired to ellect adjustable periodic reversal Therefore I do not limit it to the specific form and arrangement of the apparatus in the drawing. I claim: 1 Apparatus for actuating a rotatable device back and forth through switching means energized by hing means t0 motor as the limits sector.

5. Apparatus for actuating a. rotatable device a plurality oi' predetermined sectors, comprising a reversible drive the same, an electromagnetically-operated reversing switch for said motor, selector switch means controlling the movement of said reversing switch into "torward position and into "reverse to be actuated.

Apparatus for actuating a rotatable device back and forthl through any one of a plurality of predetermined sectors, comprising a reversible of the desired sector is reached.

9. Apparatus for actuating a rotatable device back and forth through predetermined sectors, motor connected to said any one of aplurality o! comprising a reversible said reso as to said rotatable device through a sector determined by the setting et the selector device.

10. Apparatus for actuating a rotatable denies corresponding to back and forth through any one o! a plurality of predetermined sectors comprising a. reversible motor connected to said device to drive the same. rotary switching means driven by said motor synchronously with said device, said switching means including a rotating Contact and a plurality of fixed contacts engageable by said rotating Contact, a manually-adjustable sector selectwo sets of fixed contacts each those of said rotan7 switching means, and also having two rotatable contacts adapted to be placed in engagement with the acsooiated fixed contacts according to the limits of the sector through which it is desired to actuate said rotatable device, electrically-operable means tor device having for effecting reversal of operation of said motor, and circuit connections between said rotary switching means, said sector selector device and said reversing means for controlling the latter so as to eect actuation of said rotatable device through a sector determined by the setting of the sector selector device.

FREDERICK R. FARROW, JR.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Country British Date Sept. 30, 1926 Number 

